Both IL-2 and IFN-.gamma. have demonstrated an ability to activate natural killer (NK) cell activity (1-6). A theory is that such IL-2 activity results from induction of IFN-.sub..gamma. (7,8). See also (9,10). NK cells, a component of natural cell-mediated cytotoxicity (NCMC), have been defined by their ability to lyse neoplastic cells in vitro without definable prior activation (11). IL-2 can be obtained from natural source or via recombinant DNA technology (12-17). Gamma interferon (IFN-.gamma.) has been prepared via recombinant technology as well (18,19).
Thus, the nature and tumor inhibition activity of both of these compositions is known.
It has previously been shown that IFN-.gamma. exhibits a synergistic effect with .alpha.- or .beta.-interferon in assays for cell growth inhibition (20,21), and with lymphotoxin (22).